Emissions created by the combustion of coal contribute roughly a third of the anthropogenic mercury introduced into the atmosphere each year. Once in the atmosphere, the mercury forms soluble compounds and is deposited by rain in terrestrial and aquatic environments. Once in these environments, it can be transformed by environmental reactions or by bacteria and animals into highly toxic methyl mercury (MeHg). The presence of MeHg is much more prominent in aquatic environments and tends to bioaccumulate in aquatic food webs. People and animals can be exposed to toxic levels of MeHg by eating contaminated fish. Toxic exposure can affect numerous physiological functions including immune function, genetic/enzymatic function, and neurological function and development. The consequences of increased levels of toxic mercury species in the environment are of great concern, yet anthropogenic production of mercury continues to increase.
Many different adsorbents have been tested for use in mercury removal technologies for exhaust gases. Activated carbon, though relatively expensive, is currently the most effective and commonly used adsorbent. However, the U.S. Environmental Protection Agency (EPA), the energy industry, and other interests are still searching for more cost-effective and efficient solutions.
Given the state of coal plant technology, there is a need to develop lower cost and/or more efficient technology options that will permit the effective use of the existing coal plant utilities while meeting environmental regulations. The present invention provides a clay-based adsorbent and a method for using the adsorbent that offers an efficient, abundant, recyclable, and low-cost alternative to the current methods.